Air-compressor.



PATENTED OCT. 11, 1904. S. E. ALLEY.

7 AIR COMPRESSOR.

APPLIGATION FILED JAN. 27. 1904.

' 3 SHEETS-SHEET 1.

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mmmnmlm u F Invemtorj Wutncsses PATENTED OCT. 11, 1904.

S. E. ALLEY.

AIR COMPRESSOR.

APPLICATION FILED JAN. 27. 1904.

- 3 SHEETS-SHEET 2.

NO MODEL.

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V%Mv4 No. 772,266. PAT-ENTED 001?. 11, 1904.

s. 1:. ALLEY.

AIR COMPRESSOR.

APPLICATION FILED JAN. 27. 1904. 110 MODEL. 1. 7 a SHEETS-SHEET 3.

W4 71,65,565 In we nntor':

UNITED STATES Patented. October 11, 1904.

STEPHEN EVANS ALLEY, OF GLASGOW, SCOTLAND.

AIR-COMPIQESSOR.

SPECIFICATION forming part of Letters Patent No. 772,266, dated October 11, 1904. Application filo January 27, 1904. SerialNo. 190,877. (No model.)

To all whom it may concern:

Be it known that I, STEPHEN EVANS ALLEY, a subject of the King of Great Britain, residing at Glasgow, Scotland, have invented certain new and useful Improvements in Air- Compressors, of which the followingis aspecification. 7

This invention relates to air or gas compressors, and has for its object the improvements of the distribution in compound or stage air or gas compressors of the differential-piston type.

When in an air or gas compressorasliding valve is employed operatedas, for instance, by an eccentricto receive simple harmonic motion for the purpose of controlling the distribution, it is found to operate satisfactorily as far as its regulation of the commencement and completion of the admission to each chamber of the cylinder of the compressor is coning the commencement of discharge under, for.

example, circumstances such as are above detailed or under any conditions wherein a sliding valve gives a discharge so early that the desired compression is unobtainable with the aid of the sliding valve alone an automatic non-return valve is according to this invention placed in the delivery-passage leading from the sliding valve to the receiver or reservoir to which the compressed air or gas is to be delivered, and this valve is so loaded or controlled that in spite of the premature opening by the sliding valve of the delivery-passage the said non-return valve will cause compression to occur between it and the cylinder to the desired degree before permitting the compressed charge to proceed past it to the receiver or reservoir.

, anism.

In the accompanying drawings, which illust'rate one method of carrylng out this mven- ,tion as applied to a stage air or gas compressor of the differential-piston type, Figure 1 is a plan of the compressor with its valve mech- 2 2 of Fig. 1. Fig. 3 is a diagram showing a modified construction of valve mechanism, and Fig. 4 is a diagram showing yet another modified construction of valve mechanism.

Fig. 2 isrvertical section on the line,

Like letters indicate like parts throughout the drawings.

The stage air or gas compressor shown in the drawings has a water-jacketed cylinder A, within which operates a differential or trunk piston B B,which divides the cylinder A into upper and lower compression-chambers A A respectively, and is operated bya crank-shaft E. In compressors of this type the air to be compressedis first admitted to the upper compression-charnber A and after compression in this chamber is delivered to an intermediate receiver or intercooler, from whence it is allowed to pass to the lower chamber A In this chamber it is brought to the required degree of compression and is delivered from thence for use Extending along one side of the cylinder is a valve-chest C, from which conduits C C communicate with the chambers A A respectively, of the cylinder A. Each of these conduits serves the double purpose of inlet and exhaust for its chamber.

The valve-chest is annular in cross-section and contains four coaxial pistons D D D D carried by a rod D operatively connected to an eccentric E on the crank-shaftE of the compressor. The upper end of the valve-chest is open to. the atmosphere, constituting an inlet by which air may be admitted to the low-compression chamber when the valve is operated to throw the conduit 0 intocommunication with this end of the valve-chest. Below the conduit C and on the opposite side of the pis- 'ton D from that which faces the open end of the valve-chest is an exhaust-conduit C communicating from the valve-chest to one end of an intercooler or intermediate receiver F. The intercooler F comprises a series of connected gas tight pipes, preferably watercooled, and connected at their free end with a conduit C, communicating from the intercooler to the valve-chest at a point situated between the pistons D D The inlet G is thrown into communication with the chamber A of the cylinder A when the piston D is operated to exhaust the chamber A of the cylinder, and on the opposite side of the piston D from that on which the inlet C communicates with the valve-chest is situated an eX- haust-conduit C communicating with a reservoir for storing the compressed air, but which is not shown in the drawings. Situated in the exhaust-conduit C is a non-return valve Gr, controlled bya spring G, which normally maintains the valve upon its seating G The outlet-conduit G is similarly controlled by a non-returnvalve the spring of which is indi cated atG The operation of this apparatus is as follows: As the piston B'B commences its downstroke inthe cylinder A the pistons D D D D constituting a compound sliding valve, are moveddownwardly by the eccentric E. This causes the piston Dto immediately throw the open end of the valve-chest G into communication with the conduit 0 of the chamber A, so that air is admitted to the chamber, and at the same time the conduit C of the chamber A is thrown into communication with the exhaust-conduitC? Presuming the chamber A to be charged,.this charge of air is compressed during the downstroke of the piston B B; but although the conduit is open for exhaust the charge is prevented from being delivered' into the reservoir with which the conduit' C communicates, as the spring G is made of suflicient strength to withstand the pressure exerted upon the valve G by the air compressed between it and the piston B until compressionhas reached the required degree. When, however, the air has been compressed to a degree slightly in excess of that required, the pressure of the spring G is overcome by the greater pressure exerted by the air upon the valve, so that the latter is lifted and the air passesit to the reservoir. When the piston'B-B has completed half its downstroke, the sliding valve D D D D commences its upward stroke, and as the piston B B reaches the limit of itsdownstroke the valve again assumes the position shown in Fig. 2. From this it will be seen that the commencement and-completion of the admission of air to the chamber A of the cylinder A is accurately timed, but that the commencement of deliv cry from the chamber A would occur too early if the exhaust-conduit were not controlled by the loaded valveG, although the completionof discharge from this chamber is accuratelytimed by the return movement of the piston D which closes the conduit 0 at the completion of the downstroke of the piston BB. The cylinder-piston now commences its upstroke and the sliding valve also moves in an upward direction, so that the conduit C of the chamber A is now thrown into communication with the exhaust-conduit G communicating with the intercooler F. This conduit being, however, controlled by a non-return valve similar to the valve G and loaded by the spring G prevents the delivery of the air which is now compressed between it and the rising piston B until the pressure obtained is sufficient to overcome the force exerted by the spring G when the valve is forced open and the'air passes through to the intercooler. At the same time the piston D throws the conduit C of the chamber A into communication with the inlet-conduit C from the intercooler F. This allows a charge of compressed air from the intercooler to enter the chamber A of the cylinder A as the piston B rises. When the piston B B has completed half its upstroke, the direction of movement of the compound sliding valve D D D D is again reversed, so

that the .parts once more assume the positionshown in Fig. 2 at the completion of the upstroke of the piston B B. It will be noted that here again the commencement of admission in this case to the chamber A and the completion of this admission and also the completion of the discharge from the chamber A are accurately timed by the movements of the compound sliding valve; but the commencement of discharge from the chamber A is made to occur too early by the movement of the sliding valve, which would result in the air being discharged practically without compression if the loaded non-return valve were not inserted in the exhaust-conduit C to controlthe commencement of the discharge, as described.

Although the non-return valves are shown loaded with a spring, a weightmay obviously be employed for the purpose, either secured to or operatively connected with the valve or incorporated in the body of the same.

By constructing the valve-chest C cylindrical in cross-section and employing coaxial pistons therein a very simple and inexpensive form of valve is obtained, as the whole valve-chest may be bored straight through, both ends being left open and the pistons readily inserted. The piston D constitutes a gas-tight partition dividing the valve-chest into two separate valve-chambers and avoids the extra expense otherwise incurred by boring up to a partition, say, cast in the valvechest and then boring the partition to form a gas-tight joint with the valve-rod D. The piston D serves a similar function and closes the lower end of the valve-chest without the expense otherwise incurred by a gland.

It will be understood that any convenient form of loaded non-return valve may be employed in the discharge-conduits G (1*, that shown beinga simple form by way of example.

The compound sliding valve cooperating with the non-return valves may be variously modified, two modifications being shown in ITO Figs. 3 and 4. In Fig. 3 the piston D is dispensed with and a partition shown cast in the valve-chest, although, as described above, this arrangement is more expensive in manufacture. In this figure the piston D corresponds to the piston D in Fig. 2, the cast partition D, bored to receive a piston-rod D, takes the place of the piston D, and the pistons D D correspond to the pistons D D of Fig. 2.

Fig. 4 shows a compound sliding valve to perform the same functions as those already described, but provided with three pistons D D D, respectively, only so disposed in relation to the inlet and exhaust conduits of the valve-chest as to constitute a balanced valve. In the arrangement shown in Fig. 2 the valve is balanced, as the exhaust from either compression-chamber and the admission from theintercooler always take place between two pistons. This arrangement is obviously impossible with three pistons, so that the balancing is effected by closing the ends of the valve-chest, as shown at C C Fig. 4E, and providing an outlet for an exhaust-conduit C between the upper piston D and the closed end of the valve-chest. The piston D controls the conduit Cof the compression-chamber A and throws it into communication with the exhaust-conduit G which communicates with the intercooler, or with an inlet-conduit C communicating from a source of air-supply with the valve-chest between the piston D and the next piston D. The piston D serves as a gas-tight partition dividing the valve-chest, as before, into two separate valvechambers, and in the lower valve-chamber is the third piston D controlling the conduit 0 of the compression chamber A Between the pistons D and D an exhaust-conduit C from the intercooler enters the valve-chest,

- and on the opposite side of the piston D a conduit C for the chamber A enters. The rod D, by which the pistons are carried, is enlarged at D, so that that portion of the piston D facing the end of the valve-chamber with which the exhaust-conduit (1 communicates is of smaller area than the face of the piston D which is toward the end of the valve-chamber in communication with the exhaust-conduit C It will be understood that although both the exhaust-conduits C C are controlled by nonreturn valves, such as the valve G described with reference to- Fig. 2, 'a body of air is always imprisoned between each of these valves and the pistons D D irrespective of the pistons being in such position as to cover or uncover the conduits C 0 and as the air imprisoned in the conduitC and the lower valve-chamber is compressed to a higher degree than that imprisoned in the conduit C and the upper valve-chamber thereduction of the area of that part of the piston D exposed to this pressure relatively to the area of the piston D and in proportion to this difference of pressure results in the balancing of the valve.

The sliding valve in Fig. 3 is only partially balanced, as the exhaust from the chamber A takes place between the piston D and the partition D and that from the chamber A between the same partition D and the piston D resulting in a greater pressure being exerted on the latter than on the former.

' What I claim as my invention, and desire to secure by Letters Patent, is

1. In a stage gas-compressor the combination of a diflerential trunk reciprocating piston, a cylinder divided by it into two com pression-chambers, an inlet-conduit and an adapted to open and close both conduits, a valve-operating mechanism by which that sliding valve is given simple harmonic mo tion across the conduits, a fl uid-operated valve controlling the exhaust-conduit and situated at a point therein which is farther from 'the' cylinder than is the sliding valve, means for exerting pressure upon the fluid-operated valve sufficient to normally close the exhaustconduit and so proportioned as to apply to the valve a thrust greater than that which immediately that the sliding valve opens the exhaust-conduit is exerted upon it in such a direction as to tend to open it by the air in compression in that portion of the exhaust-conduit which is between the loaded fluid-open ated valve and the piston.

2. In a stage gas-compressor the combi- IOG nation of a differential trunk reciprocating piston, a cylinder divided by it into two com pression-charm bers, an inlet-conduit and an eX- haust-conduit both terminating in one of the two compression-chambers, asliding valve adapted to open and close both conduits, a

valve-operating mechanism by which that sliding valve is given simple harmonic motion across the conduits, a fluid-operated valve controlling the exhaust-conduit and situated at a point therein which is farther from the cylinder than is the sliding valve, 'a loadingspring applied to the fluid-operated valve tending to keep it always in a position in which it closes the conduit and soproportioned as to apply to the valve a thrust greater than that i which immediately that the sliding valve opens the exhaust-conduit is exerted upon it in such a direction as to tend to open it by the air'in compression in that portion of the exhaustconduit which is between the loaded fluid-operated valve and the piston.

3. In a stage gascompressor thecombination of a differential trunk reciprocating piston, a cylinder divided by it into two com pression-chambers, an inlet-conduit and'an' exhaust-conduit appropriated to and termi mating in each of the tworzompression-cham- I bers, sliding valves adapted to open and close both conduits of eachcompression-chamber, r

a valve-operating mechanism by which the sliding valves are given simple harmonic motion across the conduits, two fluid-operated valves each controlling one of the exhaustconduits and situated at a point therein which is farther from the cylinder than are the sliding valves, means for exerting pressure upon each of the fluid-operated valves tending to keep each valve always in a position in which it closes the conduit and so proportioned as to apply to the valve a thrust greater than that which immediately that the sliding valves open the exhaust-conduit is exerted upon it in such a direction as to tend to open it by the air in compression in that portion of the exhaust-conduit which is between the loaded fluid-operated valve and the piston.

a. In a stage gas-compressor the combination of a differential trunk reciprocating piston, a cylinder divided by it into two compression-chambers, an inlet-conduit and an exhaust-conduit appropriated to and terminating in each of the two compression-chambers, sliding valves adapted to open and close both conduits of each compression-chamber,

a valve-operating mechanism by which the sliding valves are given simple harmonic motion across the conduits, two fluid-operated valves each controlling one of the exhaustconduits and situated at a point therein which is farther from the cylinder than are the sliding valves, a loading-spring applied to each of the fluid-operated valves tending to keep each valve always in a position in which it closes the conduit and so proportioned as to apply to the valve a thrust greater than that which immediately that the sliding valves open the exhaust-conduit is exerted upon it in such a direction as to tend to open it by the air in compression in that portion of the exhaustconduit which is between the loaded fluid-operated valve and the piston.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

STEPHEN EVANS ALLEY.

Witnesses:

WM. JNo. TENNANT, A. M. HAYWARD. 

